Axon guidance 2 Flashcards Preview

What are filopodia

finger like cellular outgrowths formed of F-actin bundles

What are lamellipodia

Sheet-like actin bundles that are crosslinked into a net

3

What process is present in the resting growth cone

F-actin treadmills - tubulin is dragged sporadically into the filopodia

4

What happens when the growth cone comes into contact with an attractive cue

F-actin treadmilling slows Tubulin is dragged much more dramatically into the filopodia F-actin accumulates which stabilizes the filopodium and drags microtubules into the back of the filopodium due to an actin-tubulin link

5

What is the role of semaphorins in growth cone movement

Semaphorins are a family of inhibitory guidance cues Secreted/soluble semaphorins can cause growth cones to turn or collapse - collapsing effect primarily on F-actin

6

What are the four forces of axon guidance

Contact attractionContact repulsionChemoattraction Chemorepulsion

7

What is required in order for a growth cone to grow

Axons can't grow where they can't attach - however - growth cones need substrates which are permissive for growth - not merely substrates to which they can attach

8

What is the role of laminin

A growth promoting ECM protein - localised in the optic nerve Laminin does not dictate the direction of axon growth, merely that axons can grow there

9

What is the result of of blocking the receptors for laminin

Slows down the growth of retinal axons but does not change their direction

10

Is laminin permissive for growth at all concentrations

Permissive within a specific concentration range - not permissive at low and high concentrations - permissive but not instructive

11

What is the role of semaphorins in the developing grasshopper limb -

Non permissive factor- able to channel axon growth (keep it out of regions it isn't needed)When semal function is blocked axon growth is sporadic - still reach Cx1 but other processes sent in other directions